Breast cancer is the most commonly diagnosed cancer in women, and estimates suggest that one third of breast cancer survivors are obese. The partners of obese breast cancer survivors are also likely to be overweight or obese. Being overweight or obese is associated with increased risk of disease progression, recurrence, and death for breast cancer survivors as well as poor health outcomes for partners (e.g., cardiovascular disease, impaired immune functioning, mortality). For both survivors and partners, pain, fatigue, and psychological distress are common. These symptoms can serve as barriers to healthy eating and physical activity, two behaviors necessary for weight loss and maintenance. Research suggests a significant and positive relationship between health behaviors within couples. Dyadic health behavior change interventions have demonstrated efficacy and may even be more efficacious than interventions targeting only one individual. Behavioral weight loss interventions for cancer survivors have not typically involved the partner. Further, behavioral weight loss interventions rarely address physical and psychological symptoms that are related to poor eating and inactivity. We propose to develop and test the feasibility, acceptability, and initial efficacy of a novel dyadic behavioral weight and symptom management intervention for obese breast cancer survivors and their partners. The proposed project consists of two phases. Phase I will include intervention development and refinement. Intervention development will be guided by the research team's prior work, the interdependence model of communal coping and behavior change, and information obtained from dyads participating in focus groups (N=3 focus groups, N=15 dyads). The intervention protocol will then be tested with 5 dyads to assist with refinement of intervention content. During phase II, the feasibility, acceptability and initial efficacy of the intervention will be examined. Obese brest cancer survivors in the first year following adjuvant treatment and their overweight or obese partners (N=20 dyads) will receive 6 weekly and 6 biweekly sessions for a total of 12 sessions spaced across approximately 5 months. The intervention will be provided in a couples-based format where each dyad will meet separately with the therapist. Dyads will be assessed at pre-, post-, and 3-months post-treatment. Study outcomes will be weight, symptoms (i.e., pain, fatigue, distress), eating behavior, and physical activity. Exploratory outcomes examine biomarkers (e.g., insulin, pro-inflammatory cytokines) associated with health outcomes for cancer survivors and their partners. The results of this study will provide preliminary data about the value of a dyadic intervention to decrease weight, improve diet, and increase physical activity while addressing symptoms that frequently serve as barriers to weight loss/maintenance. These findings will have the direct potential to produce significant public health benefit by impacting weight, a variable that has been consistently linked to poor quality of life and poor health outcomes.